In Europe it is of no importance who tends his hand to the other, or at what level hands are shaken. In Thailand, the lower ranking person must greet the higher ranked. He (she) is the one who starts the greeting ceremony and makes a respectful ‘wai’ by joining the palms, bringing them to the required level and lowering the head.

For a commoner the wai should be at breast level,

for a high ranking person at chin level,

for a monk at front level,

and only for the king above the head.

The older or socially more important person answers the greeting by making the same wai sign, but on a somewhat lower level.

The king doesn’t ‘wai’. Neither do monks. Sometimes, they give a modest nod while being greeted. Apart from them, everybody ‘wais’ everybody in Thailand, and always according to the social status of both persons.

A teacher is ‘wai-ed’ by his pupils or students, but on his turn ‘wais’ the school director or rector.

A lower ranking civil servant makes the ‘wai’ to the higher ranking official. Children ‘wai’ their parents. Never the other way around, which is considered as an insult!

In a restaurant or a supermarket you can expect to receive a thankful ‘wai’ after paying or while leaving. Don’t ‘wai’ in return. A smile and a word of thanks and goodbye will be highly appreciated, and sufficient.

The higher the hands are held in relation to the face and the lower the bow,

the more respect or reverence the giver of the wai is showing.

The wai is also common as a way to thank someone or apologise.

Sawasdee

The word often spoken with the wai as a greeting or farewell is sawasdee (สวัสดี). Phonetically, the word is pronounced "sa-wat-dee".

The spelling with the "s " comes from a transforming consonant, ส. This word was coined in the mid-1930s by Phraya Upakit Silapasan of Chulalongkorn University. This word, derived from the Sanskrit svasti (meaning "well-being"), had previously been used in Thai only as a formulaic opening to inscriptions.

The strongly nationalist government of Plaek Pibulsonggram in the early 1940s promoted the use of the word sawasdee amongst the government bureaucracy as well as the wider populace as part of a wider set of cultural edicts to modernise Thailand.